On-board water addition for fuel separation system

ABSTRACT

A fuel delivery system for an internal combustion engine including a fuel tank, a membrane dividing the fuel tank into at least a first and second portion, the membrane preferentially diffusing a substance from a mixture, the substance having an increased knock suppression relative to the mixture, and a controller adjusting delivery of condensed water to the tank responsive to an operating condition.

BACKGROUND/SUMMARY

Engines may operate using a plurality of different substances, which maybe separately delivered, or delivered in varying ratios, depending onoperating conditions. For example, an engine may use a first fuel(ethanol) and a second fuel (gasoline), each with different knocksuppression abilities, to reduce engine knock limitations whileimproving overall fuel economy. As another example, an engine may usefuel injection and water injection.

Various approaches may be used to store different substances on-board avehicle. For example, the different substances may be stored separatelyin different storage tanks, and thus filled separately. Alternatively,different substances may be stored in a mixed state, and then separatedon-board the vehicle to enable individual control of delivery to theengine.

One approach which allows ethanol to be separated from a blended fuelmixture is described in US 2007/0221163. In US 2007/0221163 a separatingdevice, fluidly coupled downstream of the fuel tank, is used to separateethanol from a blended fuel mixture. A series of injectors are used tosupply the separated fuel to a combustion chamber in the engine. Watermay be provided to the separating device to aid in the separation of theethanol from the blended fuel mixture. The water is recovered from theengine exhaust.

The inventor has recognized several disadvantages with this approach.For example, depending on the conditions and the amount of water in themixture, the mixture may be subject to freezing. Freezing may in turndegrade separation, as well as various components of the system.

As such, in one approach, a fuel delivery system for an internalcombustion engine including a fuel tank, a membrane dividing the fueltank into at least a first and second portion, the membranepreferentially diffusing a substance from a mixture, the substancehaving an increased knock suppression relative to the mixture, and acontroller adjusting delivery of condensed water to the tank responsiveto an operating condition.

In this way, not only is it possible to adjust the rate of separation ofa knock suppressing substance via control of condensed water delivery,but in addition it is possible to reduce risks of freezing. As oneexample, the delivery of condensed water can be reduced under conditionswhere ambient temperatures are decreased, even when increased water isneeded to aid separation.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a schematic depiction of one cylinder in the internalcombustion engine.

FIG. 2 shows a schematic depiction of a vehicle's exhaust, airconditioning, and fuel delivery systems.

FIG. 3 shows a first example method for adjusting water provided to thefuel tank.

FIG. 4 shows a second example method for adjusting water provided to thefuel tank.

DETAILED DESCRIPTION

A vehicle's engine may operate with a plurality of substances includingdifferent fuels, knock suppressing substances, etc. For example, anengine may operated with different fuels having different knocksuppressing capabilities, either due to an injection type (direct orport injection, for example), or due to fuel properties. For example,direct injection may provide increased knock suppression compared withport injection. As another example, direct injection of a fuel having anincreased alcohol concentration (as compared to another fuel) may alsoprovide increased knock suppression. As still another example, waterinjection may also be used to affect engine combustion and reduce knockunder some conditions. The water may be injected via one or moreinjectors, or mixed with one or more fuels in varying concentrations.

As described herein, various approaches are described for advantageouslyusing a membrane to selectively separate one or more substances from amixture. In one particular example, the membrane selectively transfersan alcohol (e.g., ethanol) from a mixture of gasoline and alcohol on oneside, to water (or a water/alcohol mixture) on the other side. Further,the transfer rate across the membrane may be adjusted by, for example,selectively delivering additional water to the water/alcohol mixture. Inthis way, the increased knock suppression of the water/ethanol mixturemay be separately delivered to the engine from the gasoline/alcoholmixture to thereby obtain increased engine performance while reducingknock limitations.

Referring now to FIG. 1, it shows a schematic diagram showing onecylinder of multi-cylinder engine 10, which may be included in apropulsion system of an automobile. Engine 10 may be controlled at leastpartially by a control system including controller 12 and by input froma vehicle operator 132 via an input device 130. In this example, inputdevice 130 includes an accelerator pedal and a pedal position sensor 134for generating a proportional pedal position signal PP. Combustionchamber (i.e. cylinder) 30 of engine 10 may include combustion chamberwalls 32 with piston 36 positioned therein. Piston 36 may be coupled tocrankshaft 40 so that reciprocating motion of the piston is translatedinto rotational motion of the crankshaft. Crankshaft 40 may be coupledto at least one drive wheel of a vehicle via an intermediatetransmission system. Further, a starter motor may be coupled tocrankshaft 40 via a flywheel to enable a starting operation of engine10.

Combustion chamber 30 may receive intake air from intake manifold 44 viaintake passages 42 may exhaust combustion gases via exhaust passage 48.Intake manifold 44 and exhaust passage 48 can selectively communicatewith combustion chamber 30 via respective intake valve 52 and exhaustvalve 54. In some embodiments, combustion chamber 30 may include two ormore intake valves and/or two or more exhaust valves.

Intake valve 52 may be controlled by controller 12 via a valve actuator.Similarly, exhaust valve 54 may be controlled by controller 12 viaanother valve actuator. Additionally, both the intake and exhaust valvesmay be adjusted via a common actuator. For example, during someconditions, controller 12 may operate the valve actuator to vary theopening and/or closing of the respective intake and/or exhaust valves.The valve actuator may include one or more of electromagnetic valveactuators for operating cam-less valves, a cam profile switching (CPS)actuator, variable cam timing (VCT) actuator, a variable valve timing(VVT) actuator and/or a variable valve lift (VVL) actuator to vary valveoperation.

Fuel injector 66 is shown coupled directly to combustion chamber 30 forinjecting fuel directly therein in proportion to the pulse width ofsignal FPW received from controller 12 via electronic driver 68. In thismanner, fuel injector 66 provides what is known as direct injection offuel into combustion chamber 30. The fuel injector may be mounted in theside of the combustion chamber or in the top of the combustion chamber,for example. In this example, fuel may be delivered to fuel injector 66by a fuel delivery system, shown in FIG. 2 discussed in more detailherein. Specifically fuel injector 66 may be included in fuel injectors244, shown in FIG. 2. In other examples, other suitable fuel deliverysystems may be utilized.

Additionally, in this example, a fuel injector 67 is arranged in a portof intake manifold 44 in a configuration that provides what is known asport injection of fuel into the intake port upstream of combustionchamber 30. Further in this example, fuel injectors 254, shown in FIG.2, may include port fuel injector 67.

Continuing with FIG. 1, Intake passage 42 may include a throttle 62having a throttle plate 64. In this particular example, the position ofthrottle plate 64 may be varied by controller 12 via a signal providedto an electric motor or actuator included with throttle 62, aconfiguration that is commonly referred to as electronic throttlecontrol (ETC). In this manner, throttle 62 may be operated to vary theintake air provided to combustion chamber 30 among other enginecylinders. The position of throttle plate 64 may be provided tocontroller 12 by throttle position signal TP. Intake passage 42 mayinclude a mass air flow sensor 120 and a manifold air pressure sensor122 for providing respective signals MAF and MAP to controller 12.

Ignition system 88 can provide an ignition spark to combustion chamber30 via spark plug 92 in response to spark advance signal SA fromcontroller 12, under select operating modes. Ignition system may includea battery capable of delivering electrical power to the spark plug andother systems in the vehicle. Though spark ignition components areshown, in some embodiments, combustion chamber 30 or one or more othercombustion chambers of engine 10 may be operated in a compressionignition mode, with or without an ignition spark.

Exhaust gas sensor 126 is shown coupled to exhaust passage 48 upstreamof emission control device 70. Sensor 126 may be any suitable sensor forproviding an indication of exhaust gas air/fuel ratio such as a linearoxygen sensor or UEGO (universal or wide-range exhaust gas oxygen), atwo-state oxygen sensor or EGO, a HEGO (heated EGO), a NOx, HC, or COsensor. Emission control device 70 is shown arranged along exhaustpassage 48 downstream of exhaust gas sensor 126. Emission control device70 may be a three way catalyst (TWC), NOx trap, various other emissioncontrol devices, or combinations thereof.

A condenser 256, discussed in more detail herein, may be fluidly coupleddownstream of the emission control device. Under some conditions watermay be condensed in the condenser, and removed from the condenser via apump 266, shown in FIG. 2.

Again referring to FIG. 1, controller 12 is shown in FIG. 1 as amicrocomputer, including microprocessor unit 102, input/output ports104, an electronic storage medium for executable programs andcalibration values shown as read only memory chip 106 in this particularexample, random access memory 108, keep alive memory 110, and a databus. Controller 12 may receive various signals from sensors coupled toengine 10, in addition to those signals previously discussed, includingmeasurement of inducted mass air flow (MAF) from mass air flow sensor120; engine coolant temperature (ECT) from temperature sensor 112coupled to cooling sleeve 114; a profile ignition pickup signal (PIP)from Hall effect sensor 118 (or other type) coupled to crankshaft 40;throttle position (TP) from a throttle position sensor; a key positionfrom ignition sensor 123; and absolute manifold pressure signal, MAP,from sensor 122. Engine speed signal, RPM, may be generated bycontroller 12 from signal PIP. Manifold pressure signal MAP from amanifold pressure sensor may be used to provide an indication of vacuum,or pressure, in the intake manifold. Note that various combinations ofthe above sensors may be used, such as a MAF sensor without a MAPsensor, or vice versa. As described above, FIG. 1 shows only onecylinder of a multi-cylinder engine, and that each cylinder maysimilarly include its own set of intake/exhaust valves, fuelinjector(s), spark plug, etc.

FIG. 2 shows a schematic depiction of a vehicle's fuel delivery system210, exhaust system 212, and an air conditioning system 214.

The fuel delivery system 210 may include a fuel tank 216 having a firstport 218. A selectively permeable membrane 224 may be used to separatethe fuel tank into an upper portion 226 and a lower portion 228, wherethe membrane may be enclosed by the fuel tank. In this example, thefirst port may include a fuel cap 220, a passage 222, and a valve (notshown), allowing fuel to be directed into an upper portion 226 of thefuel tank 216. In other examples, another suitable mechanism, allowing afuel or a blended fuel mixture to be directed into the upper portion ofthe fuel tank, may be used.

The substances in the blended fuel mixture of the upper portion mayinclude gasoline and an alcohol, such as ethanol, methanol, etc. Inparticular, fuel with various percentages of ethanol may be delivered tothe fuel tank. In some examples, a fuel having 10% ethanol and 90%gasoline may be delivered to the fuel tank. In other examples, a fuelhaving 85% ethanol and 15% gasoline may be added to the fuel tank. Yetin other examples, alternative substances may be used. The lower portionmay also house a mixture, such as an alcohol/water mixture.

The membrane 224 may include one or more membrane elements. A membraneelement can include a selectively permeable membrane element thatpermits at least one component of a mixture to pass through the membraneelement from the upper portion to the lower portion (or vice versa) at agreater rate than at least one other component of the fuel mixture.

As one non-limiting example, the membrane element can be configured topermit at least an alcohol component of a fuel mixture to permeatethrough the membrane element from the upper portion to the lower portionof the fuel tank. In this way, the membrane element can provide a fuelseparation function, whereby a permeant includes a higher concentrationof the alcohol component and a lower concentration of the hydrocarboncomponent than the initial fuel mixture due in part to the selectivityof the membrane element, where the term permeant may be used herein todescribe the fuel component or components that permeate the membraneelement.

In one example, the rate of separation of an alcohol from agasoline/alcohol mixture in the upper portion may be affected by aconcentration of alcohol in a water/alcohol concentration in the lowerportion.

The membrane may be configured to provide increased surface area for agiven fuel tank size. The larger surface area allows a greater amount ofalcohol to be separated from the blended fuel mixture, when desired. Inthis example, the membrane is pleated to form an accordion-likestructure. Additionally, the membrane may be supported by a poroussurface such as zirconia. In other examples, the membrane may behoneycomb-shaped. Furthermore, the membrane may include a number ofdifferent layers of membrane elements which may assist in the separationperformance.

In some examples, the membrane element may include a polymer and/orother suitable material that permits an alcohol component to permeatethrough the membrane element at a higher rate than a hydrocarboncomponent. For example, the membrane element may includepolyethersulfone that contains both polar and nonpolar characteristics,with the polar interaction dominant to an outer section of the membraneelement, which permits alcohol to permeate the membrane element to agreater extent than the hydrocarbons. Additionally or alternatively,membrane element may include a nanofiltration material that utilizesmolecule size exclusion and/or chemical selectivity to separate analcohol component from a hydrocarbon component of a fuel mixture.

Additionally, in this example, flexible joints 229 a and 229 b, arecoupled to the membrane, allowing the position of the membrane to bepassively adjusted as the volumes or relative volumes of the fluids inboth the upper and/or lower portion of the fuel tank change. In thismanner, the amount and/or relative concentration of the varioussubstances in the upper and/or lower portion of the fuel tank can beadjusted during diffusion or during refueling of the fuel tank, withoutrequiring additional space in the fuel tank. In alternate examples, themembrane may be actively adjusted via a height adjustment mechanism (notshown) in response to a change in the amount or relative concentrationof the knock suppressing substance(s) and/or gasoline in the upperand/or lower portion of the fuel tank.

While the above example describes the membrane mounted in a horizontalconfiguration, the membrane may also divide the tank in a verticalconfiguration. In such a configuration, the membrane may besubstantially fixed.

A concentration sensor 230 and a fuel gage 231 may be coupled to theupper portion of the fuel tank. The concentration sensor may beconfigured to determine the concentration of one or more substances inthe fuel blended mixture enclosed by the upper portion of the fuel tank.In other examples, a plurality of concentration sensors may be locatedin the upper portion of the fuel tank. Yet in other examples, analgorithm may be used to determine the concentration of a specifiedsubstance in the blended fuel mixture. In some examples, theconcentration sensor 230 may be positioned at a low point in the upperportion fuel tank, thereby allowing measurement of the concentration ofa specified substance to be measured when only a small amount of fuelremains in the upper portion of the fuel tank. Additional concentrationsensors (not shown) may be located in the lower portion of the fueltank, allowing the concentration of one or more substances in the lowerportion of the fuel tank to be determined.

Fuel gage 231 may be configured to determine the amount of fuel in theupper portion of the fuel tank. In some examples, fuel gage 231 may be afloat type fuel gauge. In other examples, another suitable type of gaugemay be used that is capable of determining the amount of fuel containedin one or both portions of the fuel tank. Furthermore, an additionalfuel gage (not shown) may be located in the lower portion of the fueltank, allowing the amount of substances in the lower portion of the fueltank to be determined.

A second port 232 may be fluidly coupled to the lower portion of thefuel tank, allowing a delivery of substances to the lower portion of thefuel tank. In this example, the second port may include a fuel cap 233,a passage 234, and a valve (not shown).

The lower portion of the fuel tank may be fluidly coupled to a fuel pump236 by a fuel line 238. In this example, fuel pump 236 is electronicallyactuated by controller 12. Fuel pump 236 may be coupled to a first fuelrail 240 by fuel line 242. The first fuel rail may be coupled to aseries of fuel injectors 244. In this example, fuel injectors 244 injectfuel directly into the combustion chambers of the engine 10. Further inthis example, the fuel injectors may include fuel injector 66, shown inFIG. 1. However, in other examples, the fuel injectors may include portfuel injectors and the number of injectors may be altered. The timing ofthe fuel injection may be applied in such a way to utilize the chargecooling effects of the mixture in the lower portion, thereby reducingknock limits on engine operation.

Continuing with FIG. 2, the upper portion of the fuel tank may becoupled to a fuel pump 246 by a fuel line 248. In this example, fuelpump 246 is electronically actuated by controller 12. The fuel pump 246may be coupled to a second fuel rail 250 by fuel line 252. In thisexample, the second fuel rail may be fluidly coupled to a series of portfuel injectors 254. Further in this example, one of the port fuelinjectors may include fuel injector 67, shown in FIG. 1.

Continuing with FIG. 2, exhaust system 212, capable of delivering waterto the lower portion of the fuel tank, is fluidly coupled to engine 10.The exhaust system may further include emission control device 70fluidly coupled to the engine via a duct 255. The emission controldevice may be fluidly coupled to condenser 256 via duct 257. Thecondenser allows liquid water to be collected from the exhaust stream.Fan 258 may be configured to direct cooling air 260 over and around thecondenser, affecting liquid formation in the condenser. In alternateexamples, the fan may be removed and air generated by the vehicle'smotion may be directed over and around the condenser to provide coolingair for condensation. Exhaust gases may exit the condenser through atailpipe 262.

A pump 266 may be fluidly coupled to the condenser by conduit 264. Pump266 may increase the pressure of the water in the conduit, allowingwater to be delivered to the lower portion of the fuel tank. In otherexamples, a gravity fed system may be used to deliver water to the lowerportion of the fuel tank. A filter 268 may be coupled to pump 266 byconduit 270, allowing impurities to be removed from the water collectedin the condenser. A valve 275 may be fluidly coupled downstream offilter 268 and adjusted by controller 12. Condenser 256, pump 266,filter 268, and valve 275 may be included in a water condensate system276.

Additionally or alternatively, condensate from the air conditioningsystem 214 may be collected and delivered to the lower portion of thefuel tank through conduit 272, filter 268, and conduit 274.

The fuel delivery system may be configured, under some conditions, toadjust alcohol/water concentration in the lower portion of the fueltank, to thereby adjust not only the rate of separation across themembrane, but also the freezing characteristics of the mixture. Forexample, the amount of water delivered to the lower portion of the fueltank may be adjusted responsive to operating conditions, therebyadjusting the alcohol/water concentration, and thus the freezingcharacteristics and/or the separation. The water delivered to the lowerportion may be adjusted in a variety of ways. These may include, forexample, adjusting valve 275, adjusting pump 266, adjusting cooling air260, adjusting operation of the air conditioning system, and/orcombinations thereof.

Various methods may be used to adjust the water delivered to the fueltank, such as shown in FIG. 3 and FIG. 4, for example.

Specifically, the following control method, shown in FIG. 3 and FIG. 4,may be implemented to adjust, and in some cases increase, the rate ofseparation of an alcohol, such as ethanol, from a blended fuel mixturein the upper portion of the fuel tank. Additionally, the followingcontrol method may reduce degradation or deterioration of the fueldelivery system, and increase the efficiency of the engine. Inparticular, under some conditions, the control method may reduce apossibility of freezing in the fuel tank, lines, pumps, valves, etc.

Referring now specifically to FIG. 3, it shows a method 300 that may beimplemented to adjust the rate of separation of an alcohol in the fueltank in response to a plurality of operating conditions. The operatingconditions may include: demand for knock suppression, feedback from anengine knock sensor, ambient temperature, pedal position, throttleposition, exhaust temperature, exhaust gas composition, etc.

At 312, an alcohol/water concentration in the lower portion of the fueltank is determined. In some examples, the concentration may be indicatedby at least one concentration sensor. In other examples, theconcentration may be inferred from various operating parameters.

The method then proceeds to 314, where it is determined if theconcentration of the water in the lower portion of the fuel tank isoutside a desired range, e.g, a desired range for controllingseparation, while reducing changes for freezing. In other examples, itmay be determined if the concentration of ethanol in the lower portionof the fuel tank is outside a desired range. Yet in other examples, itmay be determined if the amount of water and/or ethanol in the lowerportion of the fuel tank is outside a desired range. In some examples,it may be determined whether the concentration of water is above athreshold value, the threshold value calculated during each iteration ofmethod 300 based on various operating conditions, such as ambienttemperature. Additionally, the operating conditions may include: amountof fuel in the fuel tank, engine speed, vehicle speed, engine load,concentration of one or more substances in the blended fuel mixture,requested torque, engine temperature, etc. As one specific example, asthe ambient temperature decreases, the threshold level of water maydecreased. As another specific example, as the ambient temperaturedecreases, threshold level of ethanol may increase.

Further, the desired range of water and/or ethanol in the lower portionmay be adjusted based on a desired amount, or level, of water and/orethanol in the lower portion. In one example, the water addition may beadjusted to provide sufficient levels of a desired water/ethanol blend.

If it is determined that the concentration of water and/or ethanol is inthe desired range, the method ends.

Otherwise, the method proceeds to 316, where it is determined if theethanol and water mixture will freeze when additional water is added tothe ethanol/water mixture. In other examples, it may be determined ifthe viscosity of the ethanol and water mixture has increased beyond athreshold value. The aforementioned determinations may take into accountsuch parameters as the ambient temperature, engine temperature,concentration of water and/or ethanol, flowrate of ethanol water mixturethrough injectors, and various others.

If it is determined that the mixture is subject to freezing whenadditional water is added to the lower portion of the fuel tank, themethod proceeds to 318, where actions are taken to inhibit the additionof water to the lower portion of the fuel tank. The actions may includebut are not limited to: at 318 a, shutting down operation of pump, at318 b, inhibiting airflow over the condenser which may include stoppingoperation of fan 258 or redirecting air away from the condenser, at 318c, closing valve 275, or combinations thereof. In other examples, at 318actions may be taken to decrease the amount of water delivered to thelower portion of the fuel tank. After 318 the method returns to thestart.

If it is determined at 316 that the mixture is not subject to freezing,the method then proceeds to 320, where it is determined if the fuel tankcapacity is large enough to accommodate more water in the lower portionof the fuel tank. The aforementioned determination may take into accountsuch parameters as fuel tank volume, position of the membrane, etc. Ifit is determined that the fuel tank capacity is not large enough toaccommodate additional water, the method proceeds to 318, where actionsare taken to inhibit the addition of water to the lower portion of thefuel tank.

However, if it is determined that the fuel tank capacity is large enoughto accommodate additional water in the lower portion of the fuel tankthe method proceeds to 322, where actions are taken to add more water tothe lower portion of the fuel tank. These actions may include but arenot limited to at 322 a, driving pump 266, at 322 b, directing air overthe condenser which may include driving fan and/or redirecting air overand/or around the condenser, and opening valve 275, at 322 c. In thisway, a control method may be implemented to increase the rate ofdiffusion of a knock suppressing substance when needed, while reducingdegradation of the fuel delivery system due to various parameters suchas temperature, fuel tank volume, and various others. After 322 themethod returns to the start.

In another example, as shown in FIG. 4, additional actions may be addedto method 300, shown in FIG. 3, which may inhibit water from being addedinto the fuel tank when the addition of more water will not promote morediffusion and/or when the state of charge of a battery is below athreshold and thus may not be able to power other systems in thevehicle. Method 400 may progress in a similar approach to that shown inmethod 300. Similar acts are labeled accordingly.

Now referring to FIG. 4, at 422 it is determined if the addition of morewater to the lower portion of the fuel tank will promote more diffusionof the knock suppressing substance. If it is determined that theaddition of more water to the lower portion of the fuel tank will notpromote more diffusion, the method advances to 318. However, if it isdetermined that the addition of more water to the lower portion of thefuel tank will promote more diffusion the method advances to 424. At 424it is determined if there is sufficient battery charge to operate thepump 266 and/or fan 258, shown in FIG. 2, enabling water to be added tothe lower portion of the fuel tank. In other examples, it may bedetermined, at 424, if the battery state of charge is above apredetermined value which may take into account electrical powerconsumption of the vehicle, ignition, and various other operations. Ifthere insufficient battery charge, the method proceeds to 318.Otherwise, the method advances to 322.

In this way, control of condensate to the fuel tank is adjustedresponsive to the battery state of charge to reduce battery load fromthe fans/pumps when the state of charge is low, for example.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The specific routines described herein may represent one or more of anynumber of processing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various acts,operations, or functions illustrated may be performed in the sequenceillustrated, in parallel, or in some cases omitted Likewise, the orderof processing is not necessarily required to achieve the features andadvantages of the example embodiments described herein, but is providedfor ease of illustration and description. One or more of the illustratedacts or functions may be repeatedly performed depending on theparticular strategy being used. Further, the described acts maygraphically represent code to be programmed into the computer readablestorage medium in the engine control system.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and nonobvious combinationsand subcombinations of the various systems and configurations, and otherfeatures, functions, and/or properties disclosed herein. The followingclaims particularly point out certain combinations and subcombinationsregarded as novel and nonobvious. These claims may refer to “an” elementor “a first” element or the equivalent thereof. Such claims should beunderstood to include incorporation of one or more such elements,neither requiring nor excluding two or more such elements. Othercombinations and subcombinations of the disclosed features, functions,elements, and/or properties may be claimed through amendment of thepresent claims or through presentation of new claims in this or arelated application. Such claims, whether broader, narrower, equal, ordifferent in scope to the original claims, also are regarded as includedwithin the subject matter of the present disclosure.

1-21. (canceled)
 22. A fuel system for an engine comprising: a fueltank; a membrane dividing the fuel tank into at least a first and secondportion, the membrane preferentially diffusing alcohol from agasoline-alcohol mixture, the alcohol having an increased knocksuppression relative to the mixture; first and second fuel rails coupledon opposite sides of the membrane; and a controller adjusting deliveryof condensed water to the tank responsive to an operating condition. 23.The fuel delivery system of claim 22 wherein the alcohol comprisesmethanol.
 24. The fuel delivery system of claim 23 wherein thecontroller reduces delivery of water responsive to reduced temperature.25. The fuel delivery system of claim 24 wherein the operating conditionincludes an amount of water in the second portion of the tank.
 26. Thefuel delivery system of claim 22 further comprising a battery, theoperating condition including a battery state of charge.
 27. The fueldelivery system of claim 22 wherein the condensed water is collectedfrom an exhaust of the engine.
 28. The fuel delivery system of claim 22wherein the operating conditions include a fuel tank level of one of thefirst and second portions.
 29. The fuel delivery system of claim 22wherein the first portion contains the mixture.
 30. The fuel deliverysystem of claim 22 wherein the condensed water is gathered from an airconditioning system, and where the controller adjusts operation of theair conditioning system to adjust delivery of the condensed water. 31.The fuel delivery system of claim 22 wherein the controller furtheradjusts delivery of condensed water by adjusting a pump.
 32. The fueldelivery system of claim 22 wherein the controller further adjustsdelivery of condensed water by adjusting a flow of air over a condenser.33. An engine fuel delivery system, comprising: a fuel tank; an engineexhaust; a flexible membrane dividing the fuel tank into at least afirst and second portion, the membrane preferentially diffusing alcoholfrom a gasoline-alcohol mixture, the alcohol having an increased knocksuppression relative to the mixture; a first fuel rail coupled to thefirst portion of the fuel tank a second fuel rail coupled to the secondportion of the fuel tank; and a controller reducing delivery ofcondensed water, collected from the exhaust, to the tank responsive to areduced temperature.
 34. The fuel delivery system of claim 33 furthercomprising a battery, the operating condition including a battery stateof charge.
 35. A fuel delivery system in an engine of a vehicle,comprising: a fuel tank; a battery; a membrane dividing the fuel tankinto at least a first and second portion; a port injector coupled to afirst fuel rail coupled to the first portion; a direct injector coupledto a second fuel rail coupled to the second portion; a water condensatesystem coupled to the second portion, the water condensate systemincluding an electrically driven actuator configured to adjust deliveryof water condensate to the second portion of the fuel tank; and acontroller configured to adjust the actuator in response to an ambienttemperature and concentration of water in the second portion of the fueltank.
 36. The fuel delivery system of claim 35 wherein the actuator is apump coupled to a condenser included in the water condensate system. 37.The fuel delivery system of claim 35 wherein the actuator is a fanconfigured to direct air over a condenser included in the watercondensate system.
 38. The fuel delivery system of claim 35 wherein thecontrol further adjusts the actuator in response to a fuel level and astate of charge of the battery.